Chofu Wood Burning Water Heaters & Wood-Fired Hot Tub Systems

woodheaterThis is the perfect heater and hot tub system for cabins, those that are off grid, or if you’re simply looking for something a little more rustic or “back to basics”.

Like our regular complete hot tub systems, our wood fired hot tub systems are available in western red cedar, Alaskan Yellow Cedar or teak.

The Chofu is a precision built wood-burning water heater specifically designed for heating hot tubs. It circulates water using the principal of thermo-siphon (the movement created by rising hot water)and eliminates the need for a circulating pump or electricity.

This unique feature opens up a whole new range of possibilities for alternative hot tubs. Now you can have a traditional wooden soaking hot tub without the need for pumps or electricity.

The Chofu utilizes a sophisticated heat exchange design for efficient water heating. The stainless steel stove body surrounding the firebox is a double-walled water-jacket with a 1-inch space between. This makes the entire firebox (except the front) a heat-transferring surface.

Additional heat transfer takes place in a water-filled baffle plate that runs horizontally through the firebox. The baffle deflects the path of the fire, so it gives up more heat into the water jacket before going up the chimney.

The Chofu will connect to any tub using accessories provided flexible neoprene tubes, stainless steel pipes, and thru-wall tub ports. (Thickness of the tub wall must be specified to determine the length of thru-wall ports.)
Installation requires these four basic steps:

  1. Preparing a brick or cement foundation next to the hot tub to receive the Chofu heater.
  2. Cutting 2-1/2″ holes in the side of the hot tub for thru-wall ports.
  3. Installing pipes to connect heater and tub.
  4. Installing the stove pipe (8 feet recommended).

Operation – The Chofu operates like a conventional wood stove, achieving its fastest heating rate from dry hardwoods. It uses wood up to 17″ long and has an 18″ x 14″ x 14″ firebox. The most efficient heating comes from using 17″ x 1½” x 1½”, loaded at 45 min. intervals.

The Chofu hot tub heater has a high and low speed draft control to regulate the heating rate. It operates with the draft wide open for fast heating, and closed down to maintain temperature once the water is hot.

Features

  • High grade stainless steel stove body
  • 1/8-inch steel stove front
  • Heavy cast iron door and grates
  • Hot Tub Connection kit
  • Generous size firebox, 18″L x 14″W x 10″H
  • Vented smoke-outlet for secondary combustion.
  • ¾” drain for freeze protection.
  • An ash drawer for easy removal of ashes.
  • A long handled ash rake

Specifications

  • Dimensions: 16″ wide x 23″ long x 18″ high
  • Weight: 59-lbs.
  • Stove body: Grade 316 stainless steel, inner wall 20-gauge, outer wall 22-gauge
  • Stove Front: 1/8-inch steel
  • Firebox door and grates: cast iron
  • Firebox dimensions: 18″L x 14″W x 10″H
  • Heat exchange surface area: 9 sq. ft.
  • Smoke outlet: 4 5/8-inch (reduced to 4-inch)
  • Circulating pipes: 1¾” O.D.
  • Drain: ¾” I.D.

Heating Rate Information – Although the heating rate is variable depending on dryness and type of wood, frequency of loading, etc., the average heat output of the wood burning Chofu hot tub heater is 32,000 BTU’s (an 11kW electric heater is about 30,000 BTU’s). A 200 gallon hot tub can be heated at approx. 20ºF per hour.

Note: The heat output of the Chofu increases after an initial 45-min. warm-up period that heats the stove body and establishes a bed of coals.

Heating Rate

Hot tub size…
diameter x height
Gallons temp. rise per hour
4×4 300 14°
5×2½ 300 14°
5×3 375 11°
5×4 500
5×5* 610
6×3 600
6×4* 725
*We don’t recommend this large a hot tub due to the extended heat-up time

Most Requested Upgrades & Accessories

Stainless Steel Stovepipe – Made of grade 304 stainless steel. 8ft of pipe is necessary to produce the optimum air-draw through the stove for a fast, efficient heating rate; a shorter length will produce a slower heating time.

Using more than 8ft of pipe produces a hotter fire but will reduce fuel efficiency because more of the flame is drawn up into the chimney. Remedy this by installing a stove damper. If more than 8ft of pipe is used, it must be supported to insure stability.

Sheet metal screws and a cobalt drill bit are provided with the Chofu Wood-fired Heater for fastening stove pipe connections.

Stainless Steel Chimney Cap – Made of grade 304 stainless. Maybe necessary where danger of fire is extreme, however, secondary combustion in Chofu prevents most sparks from escaping chimney.

Adding a chimney cap reduces draw through stove, slowing the heating rate. 10ft or more of pipe is necessary when using a chimney cap, to maintain maximum heat rate. Stovepipe with a chimney cap must always be supported to provide stability.

Filtration/Circulation System – This high performance pump/filter skid pack is rated at 2400 gallons per hour and consists of an energy efficient 120v Hayward Power-Flo pump and Micro Star-Clear filter, all pre-plumbed and mounted to a molded base. Designed for outdoor applications, simply plug it into a GFCI protected outlet and add a timer if desired.